The present invention relates to a power window apparatus for use with a motor vehicle for driving a window glass for opening and closing a window using power supplied by a drive source, e.g., a motor. More particularly, the invention relates to a power window apparatus with a safety device which performs a safety control operation when the hand or neck of a driver or passenger is interposed between the window glass and the sash. In one aspect, the invention particularly relates to the structure in a power window apparatus of a drive unit including a motor.
Generally, a power window apparatus is constructed so as to drive the window glass for opening and closing purposes using a motor, for example, as shown in FIG. 2. In this figure, which schematically shows the construction of the power window apparatus, a window drive mechanism 2 is disposed under the window of a motor vehicle. In the mechanism, a rail 3 is mounted on the body frame of the motor vehicle in a vertically arrayed state. A slider 4, mounted on the rail 2, is slidable along the rail. A wire 5 is connected to the slider 4 and a drive unit 7 and is wound around pulleys 6, which are located at the top and bottom of the slider 4. When a motor contained in the drive unit 7 is driven, the slider 4 is vertically moved by the wire 5. A window glass 1 is mounted to the slider 4. With vertical movement of the slider 4, the window glass 1 opens or closes a window space defined by a sash 8.
In the power window apparatus of this type in which the window glass is automatically moved for opening and closing by the drive source, a dangerous situation occurs when the hand or neck of a passenger is interposed between the window and the sash. To cope with this, a safety device has been proposed. The safety device operates such that when it detects a state where an object is interposed between the window glass and the sash, it stops the movement of the window glass or forcibly moves the window glass in the opening direction.
To detect the state where an object is caught in the window, the safety device uses a current detector for detecting the drive current to the motor of the drive unit 7. When the object is caught in the window glass, the load of the motor increases, and hence the motor drive current increases. The drive current detector detects this increase of the motor drive current. In response to the output signal of the drive current detector when it detects the increase of the drive current, the safety device controls, for safety, the movement of the window glass so as to allow the object to be released.
The safety device as mentioned above detects the state of an object being caught in the window on the basis of the increase of the motor drive current. Before the drive current increases, some time elapses after the object is caught in the window glass. As a result, the safety control by the safety device starts, with a time lag, after the object is actually caught in the window glass. This fact implies that when the neck of a passenger is caught in the window glass, the state of the neck being caught continues until the safety device starts the safety control operation. In this respect, the safety device provides an unsatisfactory safety measure.
Another safety device has been proposed. In this device, the opening/closing movement of the window glass is constantly monitored. When the closing movement of the window glass stops at any other position than a position of the window glass where it is completely closed, the safety device decides that the window glass has caught an object. To make the decision, the safety device detects the motor speed during the opening/closing movement of the window glass, and recognizes a decrease of the motor speed on the basis of a comparison of the detected motor speed with a reference value. The safety device is improved in that it can quickly start the safety control operation.
However, the motor speed generally varies depending on ambient conditions of the motor, such as temperature and humidity. Accordingly, the safety device using the reference value cannot precisely make the decision whether or not the object is caught in the window glass when the ambient conditions vary. In this respect, the safety device is still unsatisfactory in its performance.
Moreover, in the above conventional type of power window apparatus, the direction or the speed of rotation of the motor is controlled on the basis of the results of detecting the open/close operation of the motor, viz., the rotation of the motor. To this end, a sensor device for sensing the motor rotation and a control circuit for controlling the motor rotation are provided in the power window apparatus. The sensor device and the control circuit are provided separately from the drive unit, and are mounted on the drive unit or the body frame of the vehicle. The prior art suffers from an increase in the number of required parts and complexity of the process required to assemble the power window apparatus to the body frame.